Stabilizer control devices for vehicles are configured to reduce or restrain the rolling motion of the vehicle by providing the appropriate rolling moment from the outside by the operation of the stabilizer during the turning traveling of the vehicle. A known roll stabilization system of a vehicle that includes an actuating arrangement described in Published Japanese Translation of PCT International Publication for Patent Application No. 2002-518245 includes a stabilizer bar halved on the front and the rear axle and a slewing drive arranged between halves of the stabilizer bar.
The vehicle roll stabilization system described in Published Japanese Translation of PCT International Publication for Patent Application No. 2002-518245 includes a lock means for locking the displacement to the opposite direction at the turning at a halved portion of the stabilizer in order to reduce the rolling motion beyond the adjusting range compared to the vehicle which does not includes the roll stabilization system. An electromagnetic application brake or an electromagnetic release brake is used for the locking. In case the electromagnetic application brake is used, it is ensured that adjusting actuators provided at the front axle and the rear axle are locked at the respective neutral positions for overcoming the inclination attitude of the vehicle body traveling straight when the vehicle roll stabilization system is at the failure. The halved portions of the stabilizer locked relatively each other serve as a passive torsion bar.
Notwithstanding, with the construction of the vehicle roll stabilization system described in Published Japanese Translation of PCT International Publication for Patent Application No. 2002-518245, the mechanical means such as the electromagnetic application brake and the electromagnetic release brake are required to be provided between a motor and a deceleration gear device for the locking, which is inevitable for increasing the size of the actuator. In addition, because the stabilizer bar is held at the vehicle body and end portions of the stabilizer bar are fixed at a suspension member with the actuator of the vehicle roll stabilization system, the size increase of the actuator is disadvantageous to the boarding due to the arrangement restriction when boarding the actuator at the vehicle.
A need thus exists for a stabilizer which maintains a favorable roll characteristics even when the electric power is not supplied and the stabilizer is at the failure without increasing the size of an actuator for restraining the torsional rigidity of the stabilizer.